1. Field of the Invention
The present invention relates to a communication apparatus and method which can execute half-duplex communication conforming to V.34 recommendation.
2. Description of the Related Art
Facsimile apparatuses wich communicate image data according to half-duplex communication conforming to the V.34 recommendation have been known as apparatuses of this kind.
First, a description will be provided of a normal operation in a conventional facsimile apparatus.
FIG. 2 illustrates a communication sequence in a normal operation.
(1) A calling modem transmits INFOoc and a tone B. A response modem receives these signals and transmits INFOoa, a tone A and a tone {overscore (A)}.
(2) The calling modem which has received these signals transmits a tone B, a tone {overscore (B)}, and probing signals L1 and L2. The response modem again transmits the tone A.
(3) The calling mode which has received the tone A transmits the tone B. The response modem then transmits INFOh.
(4) The calling modem which has received the INFOh stops the transmission of the tone B, shifts to phase 3, and transmits S, S, PP and TRN signals.
FIG. 3 is a flowchart illustrating such a normal operation. Since this operation conforms to the V.34 recommendation, further description thereof will be omitted.
Next, a description will be provided of a conventional recovery operation conforming to the V.34 recommendation when the calling modem at the transmission side cannot normally receive the second tone A from the response modem described in item (2), with reference to FIG. 3.
Processing in items (1) and (2) is the same as in the normal operation. Then, according to the V.34 recommendation, if the calling modem cannot detect the tone A within 2,700 ms, the calling modem transmits the tone B and awaits transmission of the tone A and the tone A. This indicates return to point x shown in FIG. 3. According to the V.34 recommendation, since the tone B is not transmitted from the calling modem, the response modem transmits the INFOh if the tone B cannot be detected while transmitting the tone A for 2,000 ms, and shifts to phase 3.
However, in the above-described conventional recovery operation, if the second tone A cannot be normally received at the calling modem, the calling modem returns to the processing of the first half portion of phase 2, and the response mode shifts to phase 3. As a result, communication cannot be recovered, resulting in error ending.
It is an object of the present invention to solve the above-described problems.
According to one aspect, the present invention which achieves the above-described object relates to a communication apparatus capable of executing a communication protocol conforming to V.34 recommendation. The apparatus includes means for detecting a second tone B signal from a calling modem for a defined time period when the second tone B signal has not been received for a predetermined time period, and means for returning a communication procedure conforming to the V.34 recommendation to phase 2 when the detection means has detected the second tone B signal within the defined time period.
According to another aspect, the present invention which achieves the above-described object relates to a communication apparatus capable of executing a communication protocol conforming to V.34 recommendation. The apparatus includes means for detecting a second tone A signal from a response modem for a defined time period when the second tone A signal has not been received for a predetermined time period, and means for returning a communication procedure conforming to the V.34 recommendation to phase 2 when the second tone A signal has been detected within the defined time period.
According to still another aspect, the present invention which achieves the above-described object relates to a communication method capable of executing a communication procedure conforming to V.34 recommendation. The method includes the steps of detecting a second tone B signal from a calling modem for a defined time period in a response modem when the second tone B signal has not been received for a predetermined time period, and returning the communication procedure conforming to the V.34 recommendation to phase 2 when the second tone B signal has been detected within the defined time period.
According to yet another aspect, the present invention which achieves the above-described object relates to a communication method capable of executing a communication procedure conforming to V.34 recommendation. The method includes the steps of detecting a second tone A signal from a response modem for a defined time period when the second tone A signal has not been received for a predetermined time period, and returning the communication procedure conforming to the V.34 recommendation to phase 2 when the second tone A signal has been detected within the defined time period.
According to yet a further aspect, the present invention which achieves the above-described object relates to a control method for controlling a modem having a function of executing a communication protocol conforming to V.34 recommendation. The method includes the steps of recognizing a state of execution of the communication protocol by the modem by reading information from a predetermined register within the modem, determining whether or not a second tone B signal from a calling modem is received by the modem for a defined time period when it is identified that the second tone B signal has not been received for a predetermined time period, when the modem operates as a response modem, and returning the communication protocol conforming to the V.34 recommendation to phase 2 to be executed by the modem when the second tone B signal has been received within the defined time period.
According to still another aspect, the present invention which achieves the above-described object relates to a control method for controlling a modem having a function of executing a communication protocol conforming to V.34 recommendation. The method includes the steps of recognizing a state of execution of the communication protocol by the modem by reading information from a predetermined register within the modem, determining whether or not a second tone A signal from a response modem is received by the modem for a defined time period if it is identified that the second tone A signal has not been received for a predetermined time period, when the modem operates as a calling modem, and returning the communication protocol conforming to the V.34 recommendation to phase 2 to be executed by the modem when the second tone A signal has been received within the defined time period.
The foregoing and other objects, advantages and features of the present invention will become more apparent from the following detailed description of the preferred embodiment taken in conjunction with the accompanying drawings.